This application relates generally to novel compounds and, more particularly, to compounds which are useful as dye developers in photographic applications.
Multicolor images formed in accordance with the principles of substractive color photography typically employ yellow, magenta and cyan image forming dyes. The yellow dye ideally transmits only green and red light and absorbs only blue light. In like manner, the magenta ("minus green") dye ideally only absorbs green light and transmits only blue and red light, and the cyan ("minus red") dye ideally absorbs only red light and transmits only blue and green light. Unfortunately, the dyes which are available for use in substractive color photography are not "ideal" dyes, but tend to absorb some of the light that they ideally should transmit. This extra absorption results in less effective reproduction by the final image of one or more colors present in the original object.
This problem may be illustrated by considering the reproduction of green light: A multicolor photosensitive element, containing a blue-sensitive silver halide layer, a green-sensitive silver halide layer and a red-sensitive silver halide layer, said silver halide layers having associated therewith, respectively, a yellow image dye-providing material, a magenta image dye-providing material, and a cyan image dye-providing material, is exposed to blue light in an amount effective to fully expose the blue-sensitive layer. Only the blue-sensitive silver halide layer is exposed; the green-sensitive and red-sensitive silver halide emulsion layers remain unexposed. If such an exposed photosensitive element were processed by diffusion transfer techniques, the yellow image dye-providing material would remain in the developed photosensitive element (negative component) but magenta and cyan image dyes would be transferred to the image-receiving layer (positive component). Since the magenta and cyan image dyes are "minus green" and "minus red" respectively, the combination of magenta and cyan dyes appear blue, i.e., they transmit blue light to the viewer and absorb green and red, thus reproducing the blue record of the original subject.
From this illustration it will be readily apparent that if either the magenta or cyan image dyes also absorb blue light, the purity and quality of the "blue image" will be impaired. In the world of practical color photography, such unwanted absorption, sometimes referred to as "tail" absorption, is the rule rather than the exception. Magenta image forming dyes typically exhibit significant absorption in the blue region.
Accordingly, there is a continuing need for new image-forming dyes for use in photography. The copending patent application of Locatell et al, Ser. No. 32,888, filed Apr. 24, 1979, now abandoned and replaced by continuation-in-part application Ser. No. 143,284, filed Apr. 24, 1980 relates to xanthene compounds which may include two silver halide developing moieties, as well as photographic film products and photographic processes employing the xanthene compounds. The present application is drawn to novel magenta dye developer compounds which include three or four silver halide developing groups and which are useful as image forming materials in photography.